Networks have a finite amount of bandwidth. As more data is transmitted over a network, transfer rates slow down and services may become unreliable. Therefore, it is advantageous to reduce the amount of unnecessary data being sent on the network.
Some data sent on networks is sent using multicast packets. Multicast packets are data segments sent to all devices on a network regardless of which devices want the data. However, networking devices that do not want the data or previously received the data simply ignore the multicast packet.